Rod deck screen with resilient material receiving section



Apri! 14, 1970 P. D. RANGER 3,506,123

ROD DECK SCREEN WITH RESILIENT MATERIAL RECEIVING SECTION Filed Dec. 6. 1968 United States Patent 3,506,123 ROD DECK SCREEN WITH RESILIENT MATERIAL RECEIVING SECTION Peter D. Ranger, Ville la Salle, Quebec, Canada, assignor to Allis-Chalmers Manufacturing Company, Milwaukee, Wis.

Filed Dec. 6, 1968, Ser. No. 781,811 Int. Cl. B07b 1/12 US. Cl. 209-395 12 Claims ABSTRACT OF THE DISCLOSURE A vibrating screen is disclosed having a deck made up of parallel rods spaced to pass therebetween particles smaller than a predetermined size. Each deck rod may be a continuous piece shaped so that the deck defines, in operating position, a descending flight of steps with each step comprising a tread and a riser. Each riser is sloped to define an angle of declination substantially steeper than adjacent treads. A transverse tie rod is arranged beneath the deck at or close to the upper end of each tread and each tie rod is carried on top of one or more vertical slats arranged with flat face portions transverse to the deck rods and having a bottom portion adapted to be connected to a screen frame. A predetermined number of the steps defined by continuous lengths of deck rods, comprising less than half of the steps, and preferably the first three steps, beginning with the top step, are provided with a steeper downward slope than the remaining steps of the flight, and these first few steeper steps are supported by flexible slats which are about 2 to 1% times taller than slats downwardly thereof and without support between the bottom portion of the slats and the tie rod on top thereof to provide greater resiliency thereof for flexing of these taller slats in vertical planes parallel to the deck rods to establish a vibrating self-cleaning action for the portion of the deck which receives the complete load of material delivered to the deck for screening and over which passes the greatest quantity of undersize material and fines.

CROSS REFERENCE TO RELATED PATENT APPLICATION This application discloses an invention applied to a vibrating screen which is also the subject of my copending United States patent application entitled Stepped Rod Deck Screen, Ser. No. 781,752, filed concurrently with this application.

BACKGROUND OF THE INVENTION Field of the invention This invention relates to material separating screens and in particular to a deck for a vibrating screen adapted to size agglomerates of sticky material such as green pellets of iron ore discharged from balling drums for drying and heat hardening into pellets that are a desired charge material for a blast furnace.

Description of the prior art US. Patents 2,750,272 of 1966; 2,925,336 of 1960; and 3,235,372 of 1966 are examples of iron ore pellet heat hardening systems which in commercial installations are provided with vibrating screens for sizing green pellets discharged from balling pans or drums for heat hardening in furnace assemblies.

It has been long known that screens having cloth decks, that is decks woven of metal or textile wires, or decks of perforated plates, are more likely to plug when screening damp sticky materials than are screens having decks of parallel rods extending in the direction of material flow. From as early as US. Patent 444,252 of 1891, heavy duty 3,506,123 Patented Apr. 14, 1970 rod deck screens were known having steps defined by rods but with alternate portions projecting upwardly that resulted in material being treated far too roughly for such a screen to be used to size water :bound agglomerates of finely divided mineral ore. Later developed screen such as shown in US. Patent 2,636,607 of 1953 are disclosed as having a rod deck assembly that handle fragile agglomerates much more gently and in which each strand is made up of several rods arranged approximately end to end. With such screens, however, sticky material tends to collect and build up where such rod segments meet. Later patents such as US. Patents 2,914,177 of 1959; 3,037,630 of 1962 and 3,289,837 of 1966 disclosed screen decks in which each strand is a single continuous piece. But screens built according to these teachings have resulted in some undesired clustering of water bound agglomerates and an accumulation of the finely divided mineral ore at locations where transverse tie rods or other support structures pass beneath the screening surface. Such accumulations act as dams that interfere with desired flow of material down the sloped screen deck and limit or reduce the capacity of the screen.

SUMMARY OF THE PRESENT INVENTION It is an object of the present invention to provide a new and improved screen with a deck of single piece rods providing a material receiving and screening section and a material outrun screening section downwardly of the material receiving section, and with the material receiving section having greater flexibility for a self-cleaning vibratory action to prevent plugging of that portion of the screen handling the greatest concentration of undersize particles and fines. Another object of the present invention is to provide a new and improved vibrating screen with a deck of single piece rods defining a downward flight of steps with the first several of the steps providing a material receiving section having greater flexibility than the remaining steps downwardly thereof for achieving a selfcleaning vibratory action and prevent plugging of the screen deck steps handling the greatest concentration of the undersize material and fines.

According to a preferred embodiment of the present invention for achieving such objects, a descending flight of steps is formed by rods parallelly spaced apart with each step of the screen deck defined by a tread and riser with each riser sloped to define an angle of declination much steeper than the downward slope of the adjacent treads. Transverse tie rods, which are necessary to hold the assembly together, are located to be beneath a free flight trajectory of pellets coming down the flight of steps and which are air borne over each riser. The location for such tie rods is beneath the deck at or close to the upper end of each tread and each tie rod is carried on top of one or more vertical slats arranged with flat face portions transverse to the deck rods and having a bottom portion adapted to be connected to a screen frame. Each step provides an unsupported span of deck rods between tie rods that is of substantially equal length. The first few spans or steps, preferably the first three, defined by continuous lengths of deck rods, have a steeper downward slope than the following spans or steps and these first three are supported by flexible slats about 2 to 1% times taller than slats downwardly thereof. These taller slats are without support between the bottom portion of the slats and the tie rod on top thereof to provide greater resiliency thereof for flexing these taller slats to bend in vertical planes parallel to the deck rods. This bending and flexing provides for a self-cleaning vibratory action for that portion of the screen which is the portion of the screen deck which receives the complete load of material delivered to the deck for screening and over which passes the greatest quantity of undersize material and fines.

Other objects of the invention and how they are attained will appear from the following description of the invention with reference to the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevation of a vibrating screen according to the present invention, with a portion of the screen body broken away to show the configuration of the deck and certain deck supporting structures; and 1 FIG. 2 is a partial view of the screen shown in FIG. 1, taken along the line IIiI in FIG. 1 and as viewed in the direction indicated by the arrows.

Referring to FIG. 1 a vibrating screen 1 is shown com prising support base members 2 and a screen body having parallel frame members 3 and crossarms 23 therebetween, resiliently mounted on the base 2 and inclined in the conventional manner. The screen body with its parallel frame members 3 and crossarms 23, is supported on base 2 and vibrates relative thereto by an assembly 4 including a vibrator 5, all of which may be constructed and arranged in the manner described in US. Patent 3,030,098 of 1962.

As shown in FIGS. 1 and 2, the screen 1 is provided with a deck assembly made up of parallel rods 11 spaced apart from each other to define therebetween a space 12 for passing particles 13 which are smaller than a size predetermined by the space 12 between rods 11, and for guiding along the tops of the rods 11, particles 14, which are larger than space 12. Each rod 11 is a single continuous piece shaped to individuaily and collectively define a descending flight of steps 15 (see FIG. 1) transverse to rods 11. Each step 15 comprises a tread 16 with a riser 17, and each riser is arranged between adjacent treads 15.

The rods 11 are supported by transverse tie rods 20 each of which, as shown in FIG. 2, is carried on top of vertical slats 21, 22 arranged with flat face portions transverse to deck rods 11. Slats 21, 22 each have a bottom portion connected to a crossarm 23 by bolts 24. Flanges 25 and 26 on the ends of each crossarrn 23 are connected by bolts 27, 28 to the frame members 3.

Referring to FIG. 1, each step 15 of a tread 16 and riser 17 provides an unsupported span of deck rods between a pair of parailel tie rods. Between each pair of adjacent treads 16, the riser 17 therebetween is sloped to define an angle of declination A below a horizontal plane 30 substantially steeper than the downward slope of the adjacent treads 16, and the angle of declination A of riser 17 below piane 30 is at least about 70 degrees. The transverse tie rods 20 beneath each step 15 is close to the upper end of the tread 16.

The first few steps 15a, 15b, 15c shown in FIG. 1 provide a material receiving zone for receiving material particles 13, 14 which may be such as green pellets of finely divided iron ore. The treads of these steps Isa-15c have a substantially steeper downward slope than the steps downwardly thereof and are supported by flexible slats 21, 22 which are progressively from to 1%. times taller than the slats downwardly thereof and beginning with the slat beneath the downward end of the step 15d. These taller slats are without support between the bottom porion of the slat and the tie rod on top thereof to provide steps 15a-15c with a greater resiliency in order that the screen will operate in the manner that will hereinafter be described.

In one preferred design of a screen according to this invention for operation in a system such as described in US. Patent 3,235,372, to size green water bound pellets of finely divided iron ore, the base 2 will be arranged to support the screen body 3 with a downward slope from horizontal of about 1=3-20 degrees. Rods 11, inch diameter may be spaced apart about 0.6 inch to size pellets at about 4; inch, which is a desired size for use in systems of the type referred to. The first few steps 15a-15c, which define a material receiving zone, may be provided with treads 16 sloping downward from horizontal in a range from about 50 degrees at the beginning of the receiving zone to perhaps as little as about 15 degrees where the receiving zone ends and joins the beginning of the material outrun portion, defined by the steps downwardly thereof.

With the steps 15a-15c supported by taller slats free of midportion support, these slats are therefore more flexible and able to bend in vertical planes parallel to deck rods 11 and provide the steps 15a15c with great resiliency. Substantially, the entire discharge from such as a balling drum (not shown) is received by the screen 1 in the area of these steps 15a*15c. Since undersize particles and fines pass through the spaces 12, each step downwardly of this receiving area handles progressively less material. This results in the receiving area 15a-15c handling the greatest quantity of undersize and fines, which being sticky, exposes this deck area to the greatest tendency to plug spaces 12. However, being more resilient than step 15d and steps downwardly from step 15d, this area 15a-15c of the deck is provided with great re siliency and flexibility to vibrate in uneven patterns as a result of blows delivered by material falling thereon, which results in complex movements of sufiicient magnitude and force to throw from rods 11 in this area, material tending or attempting to adhere to the rods. This provides a self-cleaning action for the material receiving steps 15a-15c and promotes rapid screening action.

From the foregoing detailed description or" the present invention, it has been shown how the objects of the invention have been attained in a preferred manner. However, modifications and equivalents of the disclosed concepts such as readily occur to those skilled in the art are intended to be included within the scope of this invention.

The embodiments of the invention in which an exclusive property or privilege are claimed are defined as follows:

1. A deck for a vibrating screen comprising:

(A) a plurality of deck rods parallel and spaced apart in fixed position by a plurality of transverse tie rods connected to the underside of the deck rods, and with the deck rods shaped to define in operating position a downward slope having an upper particle receiving end and a lower particle discharging end;

(B) the tie rods are arranged to be parallel 'to each other and spaced apart to provide unsupported spans of deck rods there-between;

(C) each tie rod is carried on top of at least one upwardly projecting slat arranged with flat face portions transverse to the deck rods and having a bot tom portion adapted for connection to a screen body crossarm; and

(D) a first plurality of consecutive spans of said deck rods beginning at the upper particle receiving end being supported by flexible slats having heights taller than slats supporting spans of deck rods downwardly of the first plurality, said taller slats being support free between said bottom portions and the tie rods on top thereof to provide greater resiliency to the slats of the first plurality for flexing these taller slats in vertical planes parallel to the deck rods to establish a vibrating self-cleaning action of the spans of the first plurality initiated by material to be screened falling thereon.

2: In an assembly according to claim 1, the heights of the slats supporting the first plurality of spans being within a range of 2 to 1% times taller than slats supporting spans of deck rods downwardly of the first plurality thereof.

3. In an assembly according to claim 2, the spans of the first plurality being sloped downwardly to each define a greater angle of declination below a horizontal plane than the slope of spans downwardly of the first plurality.

4. In an assembly according to claim 3, the slats supporting the first plurality of spans being progressively shorter from the upper particle receiving end toward the particle discharging end of the deck, and the spans of the first plurality each having progressively less downward slope, with the slopes of the first plurality of spans being within a range from about 50 degrees declination to about 15 degrees declination.

5. In an assembly according to claim 4, the first plurality of spans comprising the first three spans extending downwardly from the upper particle receiving end of the deck.

6. In an assembly according to claim 1, each of the rods having a shape that individually and collectively define a series of descending steps from the particle receiving end to the discharge end and comprising alternate treads and risers, and with the deck rods having a transverse tie rod beneath the upper end of each tread."

7. A vibrating material separating screen comprising:

(A) a pair of parallel frame members spaced apart from each other;

(B) a plurality of deck rods parallel to the frame members and spaced apart from each other in fixed position by a plurality of transverse tie rods connected to the underside of the deck rods, and with the deck rods shaped to define in operating position a downward slope having an upper particle receiving end and a lower particle discharging end;

(C) the tie rods being arranged to be parallel to each other and spaced apart to provide unsupported spans of deck rods therebetween;

(D) each tie rod is carried on top of at least one upwardly projecting slat arranged with flat face portions transverse to the deck rods and having a bottom portion connected to a crossarm between said frame members; and

(E) a first plurality of consecutive spans of said deck rods beginning at the upper particle receiving end being supported by flexible slats having heights taller than slats supporting spans of deck rods downwardly of the first plurality, said taller slats being=support free between said bottom portions and the tie rods on top thereof to provide greater resiliency to slats of the first plurality for flexing these taller slats in vertical planes parallel to the deck rods to establish a vibrating self-cleaning action of the spans of the first plurality initiated by material to be screened falling thereon.

8. In an assembly according to claim 7, the height of the slats supporting the first plurality of spans being within a range of 2 to 1% times taller than slats supporting spans of deck rods downwardly of the first plurality thereof.

9. In an assembly according to claim 8, the spans of the first plurality being sloped downwardly to each define a greater angle of declination below a horizontal plane than the slope of spans downwardly of the first plurality.

10. In an assembly according to claim 9, the slats supporting the first plurality of spans being progressively shorter from the upper particle receiving end toward the particle discharging end of the screen, and the spans of the first plurality each having progressively less downward slope, with the slopes of the first plurality of spans being within a range from about degrees declination to about 15 degrees declination.

11. In an assembly according to claim 10, the first plurality of spans comprising the first three spans extending downwardly from the upper particle receiving end of the screen.

12. In an assembly according to claim 7, each of the rods having a shape that individually and collectively define a series of descending steps from the particle receiving end to the discharge end and comprising alternate treads and risers, and with the deck rods having a transverse tie rod beneath the upper end of each tread.

References Cited UNITED STATES PATENTS 545,106 8/1895 Spicer 209-393 X 2,636,607 4/ 1953 Roubal 209-395 2,914,177 11/1959 Parks 209-396 3,030,098 4/1962 Roubal 209-326 X 3,307,698 3/ 1967 Hafiner 209-344 X FRANK W. LUTTER, Primary Examiner US. Cl. X.R. 209-99 

